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Reformat kpk bitbase

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Simplify and streamline the code. Verified all the
resulting bitbases are not changed.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2012-01-29 12:41:50 +01:00
parent 1a1742ac4f
commit a94fd3bbec
1 changed files with 112 additions and 160 deletions
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272
src/bitbase.cpp
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@ -25,43 +25,47 @@
namespace { namespace {
enum Result { enum Result {
RESULT_UNKNOWN, INVALID = 0,
RESULT_INVALID, UNKNOWN = 1,
RESULT_WIN, DRAW = 2,
RESULT_DRAW WIN = 4
}; };
inline Result& operator|=(Result& r, Result v) { return r = Result(r | v); }
struct KPKPosition { struct KPKPosition {
Result classify_knowns(int index);
Result classify(int index, Result db[]); Result classify_leaf(int idx);
Result classify(int idx, Result db[]);
private: private:
void from_index(int index); template<Color Us> Result classify(const Result db[]) const;
Result classify_white(const Result db[]);
Result classify_black(const Result db[]);
Bitboard wk_attacks() const { return StepAttacksBB[W_KING][whiteKingSquare]; }
Bitboard bk_attacks() const { return StepAttacksBB[B_KING][blackKingSquare]; }
Bitboard pawn_attacks() const { return StepAttacksBB[W_PAWN][pawnSquare]; }
Square whiteKingSquare, blackKingSquare, pawnSquare; template<Color Us> Bitboard k_attacks() const {
Color sideToMove; return Us == WHITE ? StepAttacksBB[W_KING][wksq] : StepAttacksBB[B_KING][bksq];
}
Bitboard p_attacks() const { return StepAttacksBB[W_PAWN][psq]; }
void decode_index(int idx);
Square wksq, bksq, psq;
Color stm;
}; };
// The possible pawns squares are 24, the first 4 files and ranks from 2 to 7 // The possible pawns squares are 24, the first 4 files and ranks from 2 to 7
const int IndexMax = 2 * 24 * 64 * 64; // color * wp_sq * wk_sq * bk_sq = 196608 const int IndexMax = 2 * 24 * 64 * 64; // stm * wp_sq * wk_sq * bk_sq = 196608
// Each uint32_t stores results of 32 positions, one per bit // Each uint32_t stores results of 32 positions, one per bit
uint32_t KPKBitbase[IndexMax / 32]; uint32_t KPKBitbase[IndexMax / 32];
int compute_index(Square wksq, Square bksq, Square wpsq, Color stm); int index(Square wksq, Square bksq, Square psq, Color stm);
} }
uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) { uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) {
int index = compute_index(wksq, bksq, wpsq, stm); int idx = index(wksq, bksq, wpsq, stm);
return KPKBitbase[idx / 32] & (1 << (idx & 31));
return KPKBitbase[index / 32] & (1 << (index & 31));
} }
@ -69,24 +73,23 @@ void kpk_bitbase_init() {
Result db[IndexMax]; Result db[IndexMax];
KPKPosition pos; KPKPosition pos;
int index, bit, repeat = 1; int idx, bit, repeat = 1;
// Initialize table // Initialize table with known win / draw positions
for (index = 0; index < IndexMax; index++) for (idx = 0; idx < IndexMax; idx++)
db[index] = pos.classify_knowns(index); db[idx] = pos.classify_leaf(idx);
// Iterate until all positions are classified (30 cycles needed) // Iterate until all positions are classified (30 cycles needed)
while (repeat) while (repeat)
for (repeat = index = 0; index < IndexMax; index++) for (repeat = idx = 0; idx < IndexMax; idx++)
if ( db[index] == RESULT_UNKNOWN if (db[idx] == UNKNOWN && (db[idx] = pos.classify(idx, db)) != UNKNOWN)
&& pos.classify(index, db) != RESULT_UNKNOWN)
repeat = 1; repeat = 1;
// Map 32 position results into one KPKBitbase[] entry // Map 32 position results into one KPKBitbase[] entry
for (index = 0; index < IndexMax / 32; index++) for (idx = 0; idx < IndexMax / 32; idx++)
for (bit = 0; bit < 32; bit++) for (bit = 0; bit < 32; bit++)
if (db[32 * index + bit] == RESULT_WIN) if (db[32 * idx + bit] == WIN)
KPKBitbase[index] |= (1 << bit); KPKBitbase[idx] |= 1 << bit;
} }
@ -102,170 +105,119 @@ namespace {
// bit 13-14: white pawn file (from FILE_A to FILE_D) // bit 13-14: white pawn file (from FILE_A to FILE_D)
// bit 15-17: white pawn rank - 1 (from RANK_2 - 1 to RANK_7 - 1) // bit 15-17: white pawn rank - 1 (from RANK_2 - 1 to RANK_7 - 1)
int compute_index(Square wksq, Square bksq, Square wpsq, Color stm) { int index(Square w, Square b, Square p, Color c) {
assert(file_of(wpsq) <= FILE_D); assert(file_of(p) <= FILE_D);
int p = file_of(wpsq) + 4 * (rank_of(wpsq) - 1); return c + (b << 1) + (w << 7) + (file_of(p) << 13) + ((rank_of(p) - 1) << 15);
int r = stm + 2 * bksq + 128 * wksq + 8192 * p;
assert(r >= 0 && r < IndexMax);
return r;
} }
void KPKPosition::from_index(int index) { void KPKPosition::decode_index(int idx) {
int s = index >> 13; stm = Color(idx & 1);
sideToMove = Color(index & 1); bksq = Square((idx >> 1) & 63);
blackKingSquare = Square((index >> 1) & 63); wksq = Square((idx >> 7) & 63);
whiteKingSquare = Square((index >> 7) & 63); psq = make_square(File((idx >> 13) & 3), Rank((idx >> 15) + 1));
pawnSquare = make_square(File(s & 3), Rank((s >> 2) + 1));
} }
Result KPKPosition::classify_knowns(int index) { Result KPKPosition::classify_leaf(int idx) {
from_index(index); decode_index(idx);
// Check if two pieces are on the same square // Check if two pieces are on the same square or if a king can be captured
if ( whiteKingSquare == pawnSquare if ( wksq == psq || wksq == bksq || bksq == psq
|| whiteKingSquare == blackKingSquare || (k_attacks<WHITE>() & bksq)
|| blackKingSquare == pawnSquare) || (stm == WHITE && (p_attacks() & bksq)))
return RESULT_INVALID; return INVALID;
// Check if a king can be captured // The position is an immediate win if it is white to move and the white
if ( (wk_attacks() & blackKingSquare) // pawn can be promoted without getting captured.
|| ((pawn_attacks() & blackKingSquare) && sideToMove == WHITE)) if ( rank_of(psq) == RANK_7
return RESULT_INVALID; && stm == WHITE
&& wksq != psq + DELTA_N
// The position is an immediate win if it is white to move and the && ( square_distance(bksq, psq + DELTA_N) > 1
// white pawn can be promoted without getting captured. ||(k_attacks<WHITE>() & (psq + DELTA_N))))
if ( rank_of(pawnSquare) == RANK_7 return WIN;
&& sideToMove == WHITE
&& whiteKingSquare != pawnSquare + DELTA_N
&& ( square_distance(blackKingSquare, pawnSquare + DELTA_N) > 1
|| (wk_attacks() & (pawnSquare + DELTA_N))))
return RESULT_WIN;
// Check for known draw positions // Check for known draw positions
// //
// Case 1: Stalemate // Case 1: Stalemate
if ( sideToMove == BLACK if ( stm == BLACK
&& !(bk_attacks() & ~(wk_attacks() | pawn_attacks()))) && !(k_attacks<BLACK>() & ~(k_attacks<WHITE>() | p_attacks())))
return RESULT_DRAW; return DRAW;
// Case 2: King can capture pawn // Case 2: King can capture undefended pawn
if ( sideToMove == BLACK if ( stm == BLACK
&& (bk_attacks() & pawnSquare) && !(wk_attacks() & pawnSquare)) && (k_attacks<BLACK>() & psq & ~k_attacks<WHITE>()))
return RESULT_DRAW; return DRAW;
// Case 3: Black king in front of white pawn // Case 3: Black king in front of white pawn
if ( blackKingSquare == pawnSquare + DELTA_N if ( bksq == psq + DELTA_N
&& rank_of(pawnSquare) < RANK_7) && rank_of(psq) < RANK_7)
return RESULT_DRAW; return DRAW;
// Case 4: White king in front of pawn and black has opposition // Case 4: White king in front of pawn and black has opposition
if ( whiteKingSquare == pawnSquare + DELTA_N if ( stm == WHITE
&& blackKingSquare == pawnSquare + DELTA_N + DELTA_N + DELTA_N && wksq == psq + DELTA_N
&& rank_of(pawnSquare) < RANK_5 && bksq == wksq + DELTA_N + DELTA_N
&& sideToMove == WHITE) && rank_of(psq) < RANK_5)
return RESULT_DRAW; return DRAW;
// Case 5: Stalemate with rook pawn // Case 5: Stalemate with rook pawn
if ( blackKingSquare == SQ_A8 if ( bksq == SQ_A8
&& file_of(pawnSquare) == FILE_A) && file_of(psq) == FILE_A)
return RESULT_DRAW; return DRAW;
return RESULT_UNKNOWN; return UNKNOWN;
} }
Result KPKPosition::classify(int index, Result db[]) { template<Color Us>
Result KPKPosition::classify(const Result db[]) const {
from_index(index); // White to Move: If one move leads to a position classified as RESULT_WIN,
db[index] = (sideToMove == WHITE ? classify_white(db) : classify_black(db)); // the result of the current position is RESULT_WIN. If all moves lead to
return db[index]; // positions classified as RESULT_DRAW, the current position is classified
} // RESULT_DRAW otherwise the current position is classified as RESULT_UNKNOWN.
//
Result KPKPosition::classify_white(const Result db[]) { // Black to Move: If one move leads to a position classified as RESULT_DRAW,
// the result of the current position is RESULT_DRAW. If all moves lead to
// If one move leads to a position classified as RESULT_WIN, the result // positions classified as RESULT_WIN, the position is classified RESULT_WIN.
// of the current position is RESULT_WIN. If all moves lead to positions
// classified as RESULT_DRAW, the current position is classified RESULT_DRAW
// otherwise the current position is classified as RESULT_UNKNOWN.
bool unknownFound = false;
Bitboard b;
Square s;
Result r;
// King moves
b = wk_attacks();
while (b)
{
s = pop_1st_bit(&b);
r = db[compute_index(s, blackKingSquare, pawnSquare, BLACK)];
if (r == RESULT_WIN)
return RESULT_WIN;
if (r == RESULT_UNKNOWN)
unknownFound = true;
}
// Pawn moves
if (rank_of(pawnSquare) < RANK_7)
{
s = pawnSquare + DELTA_N;
r = db[compute_index(whiteKingSquare, blackKingSquare, s, BLACK)];
if (r == RESULT_WIN)
return RESULT_WIN;
if (r == RESULT_UNKNOWN)
unknownFound = true;
// Double pawn push
if (rank_of(s) == RANK_3 && r != RESULT_INVALID)
{
s += DELTA_N;
r = db[compute_index(whiteKingSquare, blackKingSquare, s, BLACK)];
if (r == RESULT_WIN)
return RESULT_WIN;
if (r == RESULT_UNKNOWN)
unknownFound = true;
}
}
return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW;
}
Result KPKPosition::classify_black(const Result db[]) {
// If one move leads to a position classified as RESULT_DRAW, the result
// of the current position is RESULT_DRAW. If all moves lead to positions
// classified as RESULT_WIN, the position is classified as RESULT_WIN.
// Otherwise, the current position is classified as RESULT_UNKNOWN. // Otherwise, the current position is classified as RESULT_UNKNOWN.
bool unknownFound = false; Result r = INVALID;
Bitboard b; Bitboard b = k_attacks<Us>();
Square s;
Result r;
// King moves
b = bk_attacks();
while (b) while (b)
{ {
s = pop_1st_bit(&b); r |= Us == WHITE ? db[index(pop_1st_bit(&b), bksq, psq, BLACK)]
r = db[compute_index(whiteKingSquare, s, pawnSquare, WHITE)]; : db[index(wksq, pop_1st_bit(&b), psq, WHITE)];
if (r == RESULT_DRAW) if (Us == WHITE && (r & WIN))
return RESULT_DRAW; return WIN;
if (r == RESULT_UNKNOWN) if (Us == BLACK && (r & DRAW))
unknownFound = true; return DRAW;
} }
return unknownFound ? RESULT_UNKNOWN : RESULT_WIN;
if (Us == WHITE && rank_of(psq) < RANK_7)
{
Square s = psq + DELTA_N;
r |= db[index(wksq, bksq, s, BLACK)]; // Single push
if (rank_of(s) == RANK_3 && s != wksq && s != bksq)
r |= db[index(wksq, bksq, s + DELTA_N, BLACK)]; // Double push
if (r & WIN)
return WIN;
}
return r & UNKNOWN ? UNKNOWN : Us == WHITE ? DRAW : WIN;
}
Result KPKPosition::classify(int idx, Result db[]) {
decode_index(idx);
return stm == WHITE ? classify<WHITE>(db) : classify<BLACK>(db);
} }
} }